The stability of baseline-defined categories of alcohol consumption during the adult life-course: a 28-year prospective cohort study.05 Dec 2017
BACKGROUND AND AIMS: Studies that report the relationship between alcohol consumption and disease risk have predominantly operationalized drinking according to a single baseline measure. The resulting assumption of longitudinal stability may be simplistic and complicate interpretation of risk estimates. This study aims to describe changes to the volume of consumption during the adult life-course according to baseline categories of drinking. DESIGN: A prospective observational study. SETTING: United Kingdom. PARTICIPANTS: A cohort of British civil servants totalling 6838 men and 3372 women aged 34-55 years at baseline, followed for a mean 19.1 (standard deviation = 9.5) years. MEASUREMENTS: The volume of weekly alcohol consumption was estimated from data concerning the frequency and number of drinks consumed. Baseline categories were defined: non-current drinkers, infrequent drinkers, 0.1-50.0 g/week, 50.1-100.0 g/week, 100.1-150.0 g/week, 150.1-250.0 g/week and >250.0 g/week. For women, the highest category was defined as > 100.0 g/week. Baseline frequency was derived as 'daily or almost daily' and 'not daily or almost daily'. Trajectories were estimated within baseline categories using growth curve models. FINDINGS: Trajectories differed between men and women, but were relatively stable within light-to-moderate categories of baseline consumption. Drinking was least stable within the highest categories of baseline consumption (men: > 250.0 g/week; women: > 100.0 g/week), declining by 47.0 [95% confidence interval (CI) = 40.7, 53.2] and 16.8 g/week (95% CI = 12.6, 21.0), respectively, per 10-year increase in age. These declines were not a consequence of sudden transitions to complete abstention. Rates of decline appear greatest in older age, with trajectories converging toward moderate volumes. CONCLUSION: Among UK civil servants, consumption within baseline drinking categories is generally stable during the life-course, except among heavier baseline drinkers, for whom intakes decline with increasing age. This shift does not appear to be driven by transitions to non-drinking. Cohorts of older people may be at particular risk of misclassifying former heavy drinkers as moderate consumers of alcohol.